Sourdough gets talked about like it's a health food category of its own, which oversells it a little. It's still bread — mostly flour, water, and time. But the fermentation process it goes through does change it in a few specific, well-understood ways, and those are worth knowing rather than taking on faith.
What fermentation changes
During the long, slow rise, wild yeast and lactic acid bacteria in the starter break down some of the starches and proteins in the flour before the bread ever reaches the oven. That process lowers the dough's pH and partially breaks down phytic acid — a compound in wheat bran that can bind to minerals like iron, zinc, and magnesium and make them harder for your body to absorb.
The longer, slower the ferment, the more this breakdown happens. That's part of why an 18-hour cold ferment behaves differently in the oven — and in digestion — than a quick same-day yeasted loaf.
Where the "easier to digest" claim comes from
Some people report that naturally leavened bread sits easier with them than commercially yeasted bread. The fermentation process does partially break down gluten structures and reduce some of the FODMAPs (fermentable carbohydrates) naturally present in wheat, which may explain why some people with mild sensitivities tolerate it better. This isn't the same as being gluten-free, and it isn't a guarantee for everyone — if you have celiac disease or a diagnosed gluten intolerance, sourdough fermentation does not make wheat flour safe to eat.
The realistic takeaway
Naturally leavened bread isn't a health supplement, but the slow fermentation process does make some nutrients more available and may be gentler on digestion for some people than quick-rise bread. The biggest practical difference most people notice is flavor and texture, not a dramatic health effect — which is a perfectly good reason to choose it on its own.
A related recipe
Our Country Sourdough Boule goes through the same 18-hour cold ferment described here — you can see its full nutrition breakdown on the recipes page.